Applying SRP in Methods

SRP can also be applied at the method level. A method should perform a single task. If a method does more than one task, it should be split into smaller methods.

Violating SRP

public class UserService
{
    public void RegisterUser(string username, string password)
    {
        // Validate user
        if (string.IsNullOrEmpty(username) || string.IsNullOrEmpty(password))
        {
            throw new ArgumentException("Username and password are required.");
        }

        // Save user to database
        var user = new User { Username = username, Password = password };
        SaveUserToDatabase(user);

        // Send confirmation email
        SendConfirmationEmail(user);
    }

    private void SaveUserToDatabase(User user)
    {
        // Logic to save user to the database
    }

    private void SendConfirmationEmail(User user)
    {
        // Logic to send confirmation email
    }
}

In this example, the RegisterUser method has multiple responsibilities: validation, saving to the database, and sending an email.

Adhering to SRP

We can refactor this method into smaller methods, each with a single responsibility.

public class UserService
{
    public void RegisterUser(string username, string password)
    {
        ValidateUser(username, password);
        var user = CreateUser(username, password);
        SaveUser(user);
        SendConfirmationEmail(user);
    }

    private void ValidateUser(string username, string password)
    {
        if (string.IsNullOrEmpty(username) || string.IsNullOrEmpty(password))
        {
            throw new ArgumentException("Username and password are required.");
        }
    }

    private User CreateUser(string username, string password)
    {
        return new User { Username = username, Password = password };
    }

    private void SaveUser(User user)
    {
        // Logic to save user to the database
    }

    private void SendConfirmationEmail(User user)
    {
        // Logic to send confirmation email
    }
}

Now, each method has a single responsibility, adhering to the SRP.